Jo,
I think you are right :oops:. Some babies will take advantage of the breast and use it to put themselves to sleep. I think that depends whether a baby was ever allowed to do so in his life because I have heard from many moms on this site that their babies refuse breast if not hungry. My guess would be that if he has ever had such sleep association he may do that just to go to sleep. If he hasn't fallen asleep that way, he will probably refuse breast if not hungry. Bear in mind, this is my theory and I am not absolutely sure it is correct. My dd was nursed on demand her first 2.5 months and as she is spirited in some ways I had a hard time to get her to sleep independently. She would, for example, completely refuse to nurse if she knew I wouldn't let her fall asleep on the job.
I know that for those babies who associate breast with comfort and food it is possible to take breast when not hungry. I also know babies who never used breast for anything else but food and won't take it if not hungry, they will actually scream and get upset if mom is trying to offer the breast. So, I am sorry for my original post, because it is not always the case what I wrote in it :oops:.